The invention relates to the interconnection of pipes, and more particularly to a mechanical coupling for connecting a branch pipe to a main pipe which includes an improved multi-surface sealing gasket therebetween.
It is known to connect branch pipes to a main pipe via an opening in the main pipe, with a saddle type clamp providing an effectively sealed, and mechanically secure connection therebetween. Typical of such couplings are the style 920 and 921 outlet couplings available from Victaulic Company of America, Easton, Pa., the Assignee of the present invention, and Blakeley U.S. Pat. No. 3,999,785, whose teachings are incorporated by reference herein. As shown in Blakeley U.S. Pat. No. 3,999,785, the mechanical coupling for connecting the branch pipe through a hole in the main pipe is comprised of two opposed arcuate sections which define a cylindrical space therebetween for embracing the wall of the main pipe about the hole. One of the arcuate sections, which is intended to also receive the branch pipe, includes a concave saddle wall opening which defines a portion of a cylindrical surface having a radius generally corresponding to the outer circumference of the main pipe. The branch pipe connecting portion of the arcuate section includes a radially extending branch pipe opening which is dimensioned to overlie the main pipe opening and communicate with the saddle wall. A spigot wall surrounds the branch pipe opening, terminating at the saddle wall about the perimeter of the main pipe opening. A pressure sensitive elastomeric gasket is placed about the connection between the coupling member and the opening within the main pipe in order to provide an effective seal therebetween. The gasket is typically placed within a gasket recess of the coupling member, about the spigot wall. The gasket includes sealing surfaces which are applied against the cylindrical surface of the main pipe, spigot wall, and gasket recess. It has been determined that a sufficiently large area of the main pipe proximate the hole being connected to the branch pipe must be engaged by the gasket in order to provide an effective seal. This seal area must be of a size sufficient to compensate for possible irregularities in the pipe surface which could be caused by such factors as welds during manufacture, damage during shipment, or manufacturing tolerances. The gasket construction shown in aforementioned U.S. Pat. No. 3,999,785, as well as that utilized in the Victaulic 920 and 921 outlet couplings has provided a safe and effective seal. However the configuration of the seal has necessitated a significant increase in the overall size of the coupling to accommodate the greater sealing surface areas required with the coupling of larger pipe sizes. Accordingly, it would be desirable to reconfigure the coupling, and particularly the gasket construction and its associated sealing surfaces, such that larger pipe sizes can be connected without necessitating a significant increase in the size of the coupling.
The present invention provides an improved gasket construction, and associated sealing surfaces, which results in an extremely reliable and effective seal within the coupling between branch pipe and main pipe in a manner which maximizes the circumferential sealing surface against the main pipe without necessitating the heretofore requirement of substantially increasing the size of the coupling. Furthermore, it has been determined that the gasket construction of the present invention modifies its associated gasket recess within the saddle of the coupling member in a manner which advantageously simplifies the manufacture of the coupling, as well as the on site assembly of the gasket within the coupling.
The gasket of the present invention utilizes a novel plurality of sealing surfaces between the gasket recess within the pipe coupling member and proximate surface of the main pipe about the branch coupling hole in a manner which maximizes the effective sealing areas, while minimizing the gasket radius and depth. More specifically, the elastomeric gasket, which is of a generally saddle shape corresponding to the outer circumference of the main pipe includes three generally parallel extending, but radially spaced, circumferential seals. The first circumferential sealing surface is at the radially inward extent of the gasket, and is in contact with the outer circumferential surface of the main pipe proximate the branch pipe spigot. It provides a continuation of the coupling saddle wall. The second generally circumferential sealing surface is provided at the radially opposed outward end terminus of the gasket which is in engagement with the outward wall terminus of the gasket recess. A third generally circumferential sealing surface is radially intermediate with the first and second generally circumferential sealing surfaces and is in engagement with the coupling saddle wall. A generally radial step is provided between the second and third sealing surfaces to provide a fourth generally radial sealing surface which is in engagement with a generally radial sealing surface of the gasket recess opposite the spigot wall. By virtue of this construction, the circumferential sealing area of the first sealing surface, which is in engagement with the main pipe outer circumference, will generally correspond to the sum of the circumferential areas of the second and third sealing surfaces. This configuration permits a maximizing of the first circumferential sealing area with a minimal increase in both the diameter and depth of the sealing gasket.
Since the sealing gasket must tightly fit within the coupling gasket recess which surrounds the branch pipe spigot wall, the present invention minimizes the size of the coupling to obtain the requisite sealing area against the main pipe, as well as the depth of the gasket groove.
Additional advantages are achieved by minimizing the depth of the gasket groove. Specifically, since the coupling is typically formed of a malleable iron casting, reducing the depth of the gasket recess permits a reduction of mold draft along these coupling walls. This facilitates the removal of the casting from the mold.
As a further advantage, when the coupling is installed, the on site worker typically lubricates the gasket before placing the gasket within the gasket recess. The shape, dimensions, and mating configuration of the gasket and gasket recess in accordance with the present invention will experience less propensity of the gasket to fall out of the gasket recess during its on site installation within the coupling. Hence, in addition to providing a more compact coupling and efficient gasket seal, the present invention enhances both the manufacture of the coupling and its on site installation.
In accordance with a further feature of a preferred embodiment of the present invention, the gasket includes a radially extending annular pressure slot without its second sealing surface, (which is in engagement with the radially outward wall terminus of the gasket recess), to bifurcate this surface and provide first and second pressure responsive moveable radial wall surfaces. The first of the radial wall surfaces opposes the spigot wall. The other radial wall surface forms the opposed radial wall of the fourth sealing surface (established by the radial step within the gasket). A transmission means, which may preferably be in the form of a plurality of radial channels, extends between the first and second sealing surfaces for transmitting the pressure within the main pipe to the annular pressure slot. Thus, the pressure transmitted to the annular slot urges these first and second radial wall surfaces in sealing engagement with the opposed wall surfaces of the spigot wall and gasket groove to further optimize the effectiveness of the seal provided by the gasket construction of the present invention.
Accordingly, it is a primary object of the present invention to provide an improved multi-surface gasket seal for utilization in a coupling between a main pipe and branch pipe.
A further object is to provide such a gasket seal which permits an increase in the circumferential sealing area against the main pipe while minimizing the coupling size.
Another object of the present invention is to provide an effectively sealed mechanical coupling between a main and branch pipe, which is of compact size.
An additional object of the present invention is to provide an elastomeric sealing gasket which is of a generally saddle shape and includes three generally parallel extending, but radially spaced, circumferential seals.
Yet a further object of the present invention is to provide such an elastomeric gasket in which two of the circumferential seals are at the opposed ends of the gasket, and a third seal is radially intermediate the aforesaid seals, and is established by a radial step therebetween.
Yet another object of the present invention is to provide such a gasket for utilization in a main pipe to branch pipe coupling, which further includes an annular pressure slot to enhance the sealing forces.
These as well as other objects of the present invention will become apparent upon a consideration of the following detailed description and drawings.